Wearable computing facilitates a new form of human-computer
interaction based on a small body-worn computer system that is always
on and always ready and accessible. In this regard, the new
computational framework differs from that of hand held devices, laptop
computers and personal digital assistants (PDAs). The "always ready"
capability leads to a new form of synergy between human and computer,
characterized by long-term adaptation through constancy of
user interface.

There are five major characteristics of wearable computers:

portable while operational

The most distinguishing feature of a wearable is that it can
be used while walking or otherwise moving around. This distinguishes
wearables from both desktop and laptop computers.

hands-free use

Military and industrial applications for wearables
especially emphasize their hands-free aspect, and concentrate on
speech input and heads-up display or voice output. Other wearables
might also use chording keyboards, dials, and joysticks to minimize
the tying up of a user's hands.

sensors

In addition to user-inputs, a wearable should have sensors
for the physical environment. Such sensors might include wireless
communications, GPS, cameras, or microphones.

"attention-getting"

A wearable should be able to convey information to its user
even when not actively being used. For example, if your computer
wants to let you know you have new email and who it's from, it should
be able to communicate this information to you immediately.

always on

By default a wearable is always on and working, sensing, and
acting. This is opposed to the normal use of pen-based "Personal
Digital Assistants," which normally sit in one's pocket and are only
woken up when a task needs to be done.

The idea is to be "always ready", for example, you might look up
the definition of "wearable computer" in the encyclopedia, or you
might interact with people through the medium, while doing other
things. You might also constantly grab images into a circular buffer,
and then retroactively record something. In this way, you're always
ready, and seldom miss a good shot. Many of the defining features of
wearables are the rationale behind wanting to wear them full time:

The HMD allows you to look at the screen and also at something
in the real world. This allows you to take notes while looking at the
professor, rather than constantly glancing back and forth between
paper and blackboard. You can be reading email and still be able to
walk down the street without running into people.

Having the wearable with you is equivalent to carrying an
entire reference library with instant access. Webster's dictionary and
thesaurus are always useful to have, as well as maps and phone
books. With the jump to 5 gig drives, it would be trivial to put
Compton's encyclopedia onto the wearable and have real-time access to
a tremendous wealth of information.

All the notes you ever take -- from trips, classes, business
meetings -- are always with you. With a fast search engine, you can
pull up needed information in seconds, rather than flipping through
dusty notebooks stored in your attic. You will never have to go
hunting for a pen or piece of paper again, and never worry about
searching for that missing napkin with the new system design scrawled
on it.

In a manner similar to the development of multimedia PCs, all
consumer electronics -- Music CD players, fax machines, pagers, audio
journals -- will be integrated into the wearable design. One device
will be able to handle all forms of electronic media, whether it be
audio, visual, or wireless digital communication.

A seldom realized aspect of wearable computing is augmented
reality: the seamless integration of real and virtual
worlds. Electronically stored information is extremely useful when
overlayed over a view of the outside world. For example: captions
displayed with museum exhibits, names over faces (via face
recognition), wiring schematics associated with the current
project.

What is it used for normally? [MIT]

Most of the time spent using the wearable is found inside a text
editor -- normally emacs. Phone numbers, schedules, class notes, and
programs all can be modified or searched. With Internet access,
communication becomes very easy -- everything from real-time messaging
to full Web access using Netscape is commonplace.

Outside of this, the wearable is used just like your normal
(multimedia) desktop computer. In some cases, the wearable is used
instead of having a 'main' computer.

How often is the computer worn? [MIT]

Most people with functional systems wear it about 16 hours a
day, seven days a week. Basically, all the time except during sports,
showers, sleep, and other such activities.

Can the computer be worn in the shower or while sleeping?
[Mann]

Most of the time one wears the system during most of the waking
hours. Sometimes it is worn during sleeping, especially "crashing"
somewhere in which there is not a suitable place to undress or change
clothes. Ironically, one often becomes so accustomed to the hard disk
activity that one will wake up from a deep sleep if there is something
wrong with the system (e.g. power failure or total inactivity of the
hard drive). Current systems are not waterproof and must be removed
prior to showering. As mentioned above, with respect to the sports
test and the swim test, there are obvious limitations that make it
impossible to wear it all the time. Nevertheless, it is often worn so
much that it becomes inextricably intertwined to the wearer.

Where can it be used? [MIT]

Since one of the defining features of wearable computers is
their portability, wearables can be used anywhere a person can work
comfortably. With 8-10 hour battery life and digital cellular modems
providing internet access, working on a wearable allows the same level
of productivity just about anywhere as a conventional desktop stuck in
an office.

How long have these systems been around? [Mann]

The systems have evolved over a number of years, early versions
in the 1970s gave way to more sleek and slender systems in the 1980s,
so it's been evolving, for more than 20 years.

The standard text input device is the Twiddler (http://www.handykey.com/), a
one-handed, chorded keyboard and mouse combination. It allows fairly
rapid typing (up to 60 words a minute) in any body position. You may
also want to buy a BAT keyboard (http://www.infogrip.com/Options.007.html), to which you
can connect microswitches, so that you will be able to plug directly
into the keyboard port. You can sometimes negotiate a good deal on a
bare board (e.g. without the housing) from Infogrip.

If you're going on the cheap, use a collection of
pushbutton microswitches. These switches can be found in many old
appliances or equipment, and are often driven by camshafts. Collect
as many as you can, and try to arrange them in order of stiffness, so
that the baby finger pushes the most gentle one, while the stiffest is
at the thumb position. See http://wearcomp.org/ieeecomputer.html
for pictures of this kind of keyboard.

video

Video input has been accomplished through a wide range of
video capture devices. For still images, the Color QuickCam (http://www.connectix.com/html/hardware.html)
has been used with a great deal of success. It also works well for low
frame-rate movies.

audio

Multiple types of microphones have been used for both speech
and musical input.

The Private Eye, made by Reflection Technology, is our
primary display, able to handle 720x280 monochrome video.
Unfortunately, this display has been discontinued and a myriad of
others have fallen short of its quality. Circuit Cellar (June 1998)
describes how you can build a cheap display from a viewfinder salvaged
from a broken video camera. You can also check out http://wearcomp.org/head-mounted-displays.html

audio

We have a SoundBlaster compatible PC104 board , and a variety
of speakers.

other

Tons of other output devices are being played with:
PalmPilots, tactile feedback,
speech, just to name a few.

There are many good video camera viewfinders that can display 24
rows of 80 characters. While many of the modern LCD viewfinders are
not capable of 80x24 text, there are a good many older black and white
viewfinders that can display a sharp and clear 80x24 screen, and many
can be had for $10 or less. As a parts scavenger, just be on the
lookout for studio quality video cameras.

How can you see a display that close to your eye? [MIT]

Most HMDs appear to be farther away than they actually are. For
example, when you look into the PE, you see the equivalent of a 15"
monitor at about two feet away.

How long do the batteries last in a wearable? [Mann]

Batteries are generally swapped once, twice, or maybe three
times a day, depending on how much equipment is being used at any
given time. Most computers run about eight hours on a single
charge.

Why isn't speech recognition used for input? [Mann]

Early systems, in the 1970s, were voice controlled, but more
recently it has been found that voice control is unsuitable for most
occasions. Besides the fact that people will think you're strange
when you talk to yourself, it is very impolite to speak while others
are speaking. For example, in class, if you use it to take notes, you
would be disrupting others with your speech. You may not always merely
want a transcript (or recording) of what the instructor is saying, but
often you will want to record your own thoughts that may be triggered
by what the instructor has said. For this, you would want a medium of
your own that can be used unobtrusively.

Doesn't the movement wreck the hard drive? [Mann]

Many hard drives commonly used in laptop computers can withstand
100G operational shock. It is common to go jogging while editing, and
sometimes to shoot documentary video while on horseback or riding a
mountain bike down the center of a railway line, bumping over every
railway tie, and capturing the experience on a hard drive.

What challenges remain in making the wearable suitable for
constant use?

It was said that the three tests of personal imaging would be:

the casino test

the sports test

the swim test

The underwearable made it possible to shoot documentary videos
in gambling casinos, and it has been ruggedized to the point where it
can be used in some sports, but the swim test probably remains as the
most difficult of these three.

The displays can actually be very comfortable to use for extended
durations. The virtual image of the display is quite far away, and in
fact, if it is adjusted so that parallel rays of light enter the eye, then one
experiences light equivalent to an infinitely large image, infinitely
far away. The focus can be adjusted from 10" to infinity, allowing
almost ideal viewing focus. No vision problems have been noticed
after five years of heavy use. Eye damage from excessively bright
light, over extended time periods, is however still a possibility, but
dark glasses can help to minimize the quantity of light needed to
balance with the ambient light.

Does the vibration of the PE (one of the HMDs) get annoying?
[MIT]

After wearing the PE for a few hours, the noise and vibration
really isn't noticed. It's equivalent to the hum of most computer
monitors and the fan noise - you stop being aware of them after a
while.

Can I lead an active lifestyle while wired? [Mann]

Early systems of the 1970s were quite cumbersome and delicate.
Although they were sometimes worn while playing road hockey, or the
like, they were delicate and not suitable for rough sports.
Durability and unrestrictiveness have been partly addressed but truly
durable construction still remains as a challenge.

Can you actually type while walking or jogging? [Mann]

Yes, with a properly designed keyboard, you can type while
walking around, jogging, running, or doing other activities. Typical wearcomp
keyboards are held in one hand and are easy to use, leaving the other
hand free.

Doesn't the computer get hot while you are wearing it?
[Mann]

One thing that comes to mind, that might not at first be
obvious, is that one adapts to the heat produced by the apparatus.
After several years, the body's metabolism slows down, and resting
heart rate is much lower. This condition is similar to someone who
has an "athletic heart", or someone who comes from a warm climate in
which the blood has "thinned". Normally the body operates
inefficiently, but with the device on, producing waste heat, the body
reduces its heat dissipation. The only way for the body to reduce its
production of waste heat is to become more efficient, or "athletic".
Thus even when one does not engage in a great deal of physical
activity, one becomes more similar to an athlete in one's body efficiency.

A related side-effect of wearing the apparatus for many years
is that one becomes unable to tolerate cold when removing the device,
and tends to need to wear heavy clothing in place of the device, even
when it is not extremely cold. On very cold winter days, the
difference is not so noticable (e.g. since it is additive not
multiplicative), but the difference between a "cyborg" who has taken
off the machine, and someone who doesn't normally wear the machine, is
most evident in the summer time, where the cyborg will be found
wearing long-sleeved shirts. Also the difference between the cyborg
and the non-cyborg is not so evident during physical activity as it is
during sleeping. The cyborg who has stripped off the machine will
need more blankets than the non-cyborg during sleeping, but during
active moments, the two will be approximately the same (except perhaps
the cyborg who has recently removed the apparatus will be better able
to run farther on a hot day).

Covert wearcomp/wearcam systems developed in the early 1990s
took an important first step toward making it possible to look normal
and be connected. Currently the so-called "underwearable computer"
makes it possible to be wired without looking weird.

Does typing distract or annoy other people? [Mann]

The loud clicky switches of the 1970s and 1980s have given way
to much quieter soft-touch switches. Modern one-handed keyboards can
be much quieter than the quietest of soft-touch laptop computer
keyboards. Moreover, since you can hide your hand under the table or
in a pocket, the typing sounds are that much more diminished, as is
the distracting movement of the hand.

Does airport security pose a problem? [Mann]

It is interesting the manner in which the paranoia has increased
together with the reduction in size of the apparatus, and so what is
most notable, is that there has been a roughly constant level of
aggravation at the airport. As the apparatus has gotten smaller, over
the years, so too has the paranoia level gotten higher. Words like
"lead-acid" and "lithium ion" are frightening to them -- it's better
to call them "camcorder batteries" when they ask what kind of
batteries they are. They'd like it to go in the cargo hold (e.g. as
checked luggage), or at least off-body (carry-on rather than wear-on).
If you wear it, expect to find yourself sometimes in a private search
area in your underwear, pulled back, or the like, and the nose of a
specially trained dog at the point of contact between your body and
the apparatus. Sometimes one may be asked to shut down during takeoff
and landing. One might half-expect "please turn off all pacemakers
during takeoff and landing". It's been a lot better, working directly
with the FAA, on what's acceptable. It kind-of ruins the experiment
if you've got to strip it off and lose data (e.g. if keeping a
year-long ECG, respiration, video, etc. record), but they're paranoid
about emissions during takeoff and landing.

There are actually two mailing lists devoted to this subject.
The more active of the two is wear-hard@haven.org. To
subscribe, send an e-mail to wear-hard-request@haven.org
with the text "subscribe" in the body. This list deals mainly with
the construction of wearable computers.

Is there a newsgroup on wearable computing?

On 6 June 1998, comp.sys.wearables came into
existence. This is a moderated group that deals with all aspects of
wearable computing.